I wanna build the loader, but don't know how

As topic, I just wanna build the bin with different configuration, like UART 4, different baud rate, any way or guide to build rk3308_loader_ddr589MHz_uart0_m0_v2.06.136sd.bin? or it’s just the same uboot?

rk3308_loader_ddr589MHz_uart0_m0_v2.06.136sd.bin

You can refer to the official u-boot guide:

https://github.com/u-boot/u-boot/blob/master/doc/board/rockchip/rockchip.rst

ROCKCHIP_TPL is the path for the ddr.bin

export ROCKCHIP_TPL=../rkbin/bin/rk33/rk3308_ddr_589MHz_uartX_mY_v2.07.bin

got and built, thanks